1. Field of the Invention
The invention relates generally to a product-forming roving process for use with fiberous materials, and more particularly to a microprocessor-controlled product roving system for automatically controlling the winder speed and acceleration and automatic strand insertion in a product forming roving process.
2. Statement of the Prior Art
Today's product roving systems must provide a low-cost efficient method or rapidly producing relatively high quality product packages which are uniform throughout and which do not give away excess product material and yet always include the proper number of strands to meet the high quality control standards of today's customers. Modern product roving systems must be flexible and able to quickly and efficiently switch to forming product packages of different grades and diameters of fibers and having different numbers of strands and package sizes or weights which are required by customers. Therefore, today's product roving systems must provide means for monitoring the number, length and speed of the operating strands which are being wound together to form the product while controlling winding speed and acceleration to avoid breakage yet assure that the packages are produced in the shortest possible period of time without sacrificing quality. Producing such a product roving system capable of meeting all of today's requirements poses many difficult anddiverse problems.
Due to the fragile nature of the individual strands and the number of strands involved in a typical product-forming process, it is imperative that strand replacement by accomplished manually while allowing for some mechanization to keep the process going while the broken strand or strands are being replaced. In a system utilizing twenty or more strands, it is very inefficient to stop the entire roving process in order to replace a single broken strand, yet it is absolutely imperative that the broken strands be replaced in order that the desired number of stands required to form the particular product package selected are wound during the roving process. Therefore, a strand insertion system which can automatically insert standby strands when a break or "end out" condition is detected is necessary as is a means for monitoring the number of operating strands actually being gathered together and wound for winder speed control purposes.
Furthermore, various product packages require the different numbers, grades and/or diameters of individual strands be wound and hence breaks in such strands which required the substitution of standby strands necessarily produce serving packages having diverse lengths of strands remaining thereon. Thus, there is a need for monitoring the length of each strand remaining on the various serving packages and/or for monitoring the presence or absence of the operating strands actually being wound for counting same to provide a strand insertion system for automatically inserting standby strands previously prepared by an operator to allow the roving process to continue regardless of strand run-out due to the divergent lengths of strand remaining on the various serving packages or to actual breaks in one or more of the operating strands themselves.
Another problem area in high speed roving systems relates to the speed and acceleration with which the winder or collect collects the strands. As the product forms, the linear feed-out speed from each individual serving package increases if the winder turns the collect at a constant speed. The effect of this procedure is to produce a high speed pull-out or take-out from each serving package which can produce sufficient strain to cause the individual strands to break. Another area of concern occurs at the initial start-up of the system since too rapid a start may produce a sharp pull on some of the strands causing breakage or equipment damage at the onset of the operation. Coupled with this is the fact that the efficiency and therefore the profitability of the roving process depends on the speed with which it can produce each individual process, but again, this must be weighed against the fact that modern customers for the various product packages require a high quality uniform package.
The prior art teaches several possible approaches to combat the start-up problems detailed above, none of which is truly efficient or cost effective. One prior art approach controls the winder speed at start-up to such an extent that the tension on the strands is individually built up over a long period of time so as not to produce any sudden acceleration or tension at all. This results in the slow and inefficient production of the product package and is commercially unacceptable. Another prior art solution involves the detection of the number of strands running as compared to the number of strands desired to be wound to form a particular product package and includes means for substituting standby strands into the system while continuing to wind the collet in order to avoid not only the time delay involved in stopping the system and restringing strands but also to avoid the associated tension problems associated with each individual start-up. The greater the number of times the system has to be restarted, the greater will be the chances that one or more of the strands will break during start-up. This system however, is not fully effective since it is directed to solving a particular problem and does not provide all of the status indication of the present system together with automatic insertion, multiple standby strands, an automatic shut-down, when required.
Still another problem area involves the tensioning of the strands and the breakage which can be produced when the tension becomes too great. When the product package being formed becomes larger in size or diameter, the motor speed must be controlled so that as the product package becomes larger, the winding speed decreases proportionately so that there is a constant or near constant linear take-out speed of the individual strands from the serving packages. Likewise, the tension on each individual strand is determined by the total number of strands actually running or being wound to form the product and each product selected to be formed may require a different number of operating strands to be wound. Therefore, an accurate count of the number of operating strands running is useful not only for the purposes of inserting standby strands automatically when the counted number of operating strands is different from the desired number of strands required for forming the product package, but is also useful in determining the amount of tension on the individual operating strands themselves.
Each of the problems of the prior art discussed above, taken alone, may allow for one or more solutions which provide varying degrees of acceptability, and in one form or another, many proposed solutions have been offered by the prior art. However, no attempt has been made to solve all of the above-discussed problems by providing control over the entire roving process. The need for a common control system which controls automatic strand insertion, tension, and winder speed and acceleration is essential for modern high quality, high efficiency roving processes.
It has been a practice of the prior art to produce a composite roving by withdrawing individual strands or rovings from serving packages held in creels and then converging the strands or rovings into a group and winding the group on a rotatable package tube or collet. It has been found that one of the major problems in producing such a composite linear product is (1) maintaining a positive end count on the number of operating strands actually being wound and (2) controlling the speed and acceleration at which the strands are fed out from their serving packages. The specifications for today's product packages vary significantly but there has been an ever-increasing requirement for greater accuracy in maintaining a predetermined exact number of rovings or strands wound to form a uniform, quality composite product. Thus, a need for increased reliability, durability and control to meet the more stringent requirements for producing today's composite quality rovings with an exact end count is real, and is yet, unfulfilled.
Apparatus has been used in the prior art that performs an end count function as an incidental control and effects a strand tensioning to provide a composite roving made up of individual rovings having a substantially uniform tension. In U.S. Pat. No. 3,361,375 which issued on Jan. 2, 1968, an end count was provided by a gravity-controlled drop member or a drop bar held in an elevated position by the tension on the roving threaded through a guide in the drop member itself. When the roving broke or an end out condition occurred, the drop bar would physically fall to close a switch and stop the winding motor to shut down the process. While the above-described approach was satisfactory for its intended purpose, it could not be used with the high speed creel systems of today where higher efficiency and quality are required.
As a further solution to these problems, U.S. Pat. No. 4,010,908 which issued on Mar. 8, 1977 provided an apparatus for linearly advancing a continuous strand element and directing a beam of light on the element. Reflected light therefrom was monitored and a change in the intensity of the light reflected from the strand element was used as an indication of a corresponding change in the speed of advancement of the element. This indication was used to control the linear advancement of the element itself. In other words, an optical sensing means was used not only to detect the presence or absence of the strand, but was also used to sense strand movement within predetermined limits. Once the presence or absence of the various strands and the motion thereof was detected, a problem arose as to how to translate that information into useful control signals and a second problem arose as to how to deliver new strands when a break or "end out" condition was detected.
A method for disabling the strand delivery means after cessation of motion of a predetermined number of linear bodies was required and this solution was suggested in U.S. Pat. No. 3,792,861, which issued on Feb. 19, 1974 and taught a method of combining groups of bundles of filaments, strands or rovings into composite group or roving in packaging the composite group by winding in a manner controlled by the positive sensing of each individual strand by monitoring the motion thereof.
Another area of the prior art involved in trying to produce a reliable packaging system wherein the winding motor speed could be controlled as a result of the detection of the motion or presence of individual strands. A motor speed control system using SCR power control circuits for accurately controlling the phase angle or firing point in order to accurately control the armature current to selectively increase or decrease the speed of the motor was developed to solve this problem. Silicon control rectifiers for use in various switching and control applications are known in the prior art and it is also known to use the phase angle or firing point in the positive or negative half-cycle of the AC wave form at which the SCR is switched to control the motor speed. When the SCR control circuits are digitally constructed, a dithering of the controlled motor provides a highly reliable, fast and accurate response to the generated speed control signals.
The prior art failed to find a commercially acceptable solution to all of these problems that are in a single system and the problem of determining the required motor speed of operation for a particular product package desired to be formed while monitoring and assembling the signals to control the insertion of new strands as well as to control the speed and acceleration of the motor have not been totally successful. For this particular problem, one strand package must be replaced by an operator while allowing the roving process to continue uninterrupted. Furthermore, there must be a method of changing variables whenever a new product package is to be formed which may have a different composition of strands, both number and/or diameter; a different winding speed and/or acceleration; and a different end size for the product package, measured in terms of weight, diameter, strand yardage wound, or the like. While most of these problems have been addressed separately in the prior art, no single system exists for efficiently and reliably producing a variety of desired product packages with a smooth transition when switching from one type of package to the the next or when changing any of the above-discussed variables or requirements.
The present invention solves substantially all of these problems in a single system by using a microprocessor-based control system with new and unique methods of integrating the output of various sensors with data stored in the computer to effectively control the entire product roving operation, including strand insertion, tension, and the control of winder speed and acceleration while providing status information to the operator for management or control purposes, as desired.